A conventional commercial aircraft generally includes a fuselage, a pair of wings, and a propulsion system that provides thrust. The propulsion system typically includes at least two aircraft engines, such as turbofan jet engines. Each turbofan jet engine is mounted to a respective one of the wings of the aircraft, such as in a suspended position beneath the wing, separated from the wing and fuselage. Such a configuration allows for the turbofan jet engines to interact with separate, freestream airflows that are not impacted by the wings and/or fuselage. This configuration can reduce an amount of turbulence within the air entering an inlet of each respective turbofan jet engine, which has a positive effect on a net propulsive thrust of the aircraft.
An additional aircraft engine can be integrated into, e.g., a vertical stabilizer of the aircraft to provide additional thrust for the aircraft. Each of the aircraft engines provided, including the underwing mounted aircraft engines and vertical stabilizer-integrated aircraft engine, are all sized to provide substantially identical amounts of thrust when operating at maximum capacity. Moreover, each of the aircraft engines are sized such that when operated, the cumulative amount of thrust is sufficient for the aircraft to takeoff normally.
Thus, with such a configuration, it is necessary that each of the aircraft engines be capable of operating properly in order to complete a flight mission. For example, with such a configuration, the aircraft is not able to takeoff normally without the underwing mounted aircraft engines and the vertical stabilizer-integrated aircraft engine all operating properly. Thus, the vertical stabilizer-integrated aircraft engine, while increasing a total thrust of the aircraft, may also increase the likelihood that the aircraft will be grounded due to mechanical problems.
Therefore, a propulsion system for an aircraft having an engine separate from the underwing mounted aircraft engines capable of contributing to a net thrust for the aircraft without increasing an opportunity for the aircraft be grounded due to mechanical problems would be useful. Specifically, a propulsion system for an aircraft having an engine separate from the underwing mounted aircraft engines capable of contributing to a net thrust for the aircraft (or other benefits) that is not required to operate for the aircraft to takeoff normally would be particularly beneficial.